Track 1: Emerging Technologies in Space

Paper and Podium Presentation

AuthorsTitle
1D. NikitaevAIR AND SPACE THERMAL ROCKET ENGINE WITH TURBOJET (ASTRET)
3D. K. Bond, B. Goddard, S. Bilbao Y. Leon, R. C. Singleterry, Jr.COMPARING THE EFFECTIVENESS OF POLYMER AND COMPOSITE MATERIALS TO ALUMINUM FOR EXTENDED DEEP SPACE TRAVEL
4S. WhalenHIGH PERFORMANCE LIGHTWEIGHT MATERIALS MADE BY SHEAR ASSISTED PROCESSING AND EXTRUSION (SHAPE)
5B. TaylorHYBRID FUEL COUPLING IN A PULSED Z-PINCH ROCKET ENGINE
6D. KramerNUCLEAR HEAT SOURCE CONSIDERATIONS FOR AN ICY MOON EXPLORATION SUBSURFACE PROBE
7N. D. Gaffin, S. J. Zinkle, K. M. BenenskyREVIEW OF IRRADIATION HARDENING AND EMBRITTLEMENT EFFECTS IN REFRACTORY METALS RELEVANT TO NUCLEAR THERMAL PROPULSION APPLICATIONS

Lightning Talk

AuthorsTitle
2C. Painter, C. Lavender, J. VineetPROCESS DEVELOPMENTS IN FABRICATING U-10MO PLATE FUEL

Paper and Podium Presentation

AIR AND SPACE THERMAL ROCKET ENGINE WITH TURBOJET (ASTRET)

D. Nikitaev nikitaev@unlv.nevada.edu
NTP relies on the high temperatures of fission to heat a propellant to produce thrust and may be applied to both jet and rocket engines. These types of engines were explored by projects NERVA and NEPA; however, the materials of that time were too heavy for aerospace vehicles. Today, materials such as high entropy alloys allow for such technologies to succeed, and a merging of the NEPA and NERVA designs resulted in ASTRET. Multiphysics modeling and a parametric study have shown that delivering a 70-ton payload into orbit by a single-stage spaceplane is not only possible, but cheaper than current launch vehicles after incurring the initial research costs. A spaceplane utilizing two ASTRET engines requires 2,500,000 liters of hydrogen propellant with a heavy gaseous seed such as krypton. The added molecular weight of the seed allows for a smaller propellant tank, an increase in the overall change in velocity, and a decrease in the fluid\'s specific heat capacity at the expense of some of the specific impulse. The temperatures inside ASTRET have been kept at modest levels and are below the maximum ratings of the selected materials. In the lower atmosphere (<25km), ASTRET uses a closed nuclear cycle which limits the radiation coming out of the nozzle and may be declared safe by the regulatory environment. This study was part of an undergraduate senior design project and more work must be done, including CFD modelling and verification of calculations, to declare that this engine has real world application.
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COMPARING THE EFFECTIVENESS OF POLYMER AND COMPOSITE MATERIALS TO ALUMINUM FOR EXTENDED DEEP SPACE TRAVEL

D. K. Bond, B. Goddard, S. Bilbao Y. Leon, R. C. Singleterry, Jr. bonddk@vcu.edu
Since the last Apollo mission in 1972 there have been no manned missions into deep space. There are many causes, both political and scientific, but to successfully extend manned missions towards Mars, radiation protection must be in place to shield astronauts from the two primary sources of space radiation: GCRs and SPEs. The research evaluates the shielding capabilities of various polymer and composite materials comparing them to liquid hydrogen and aluminum. Each material is evaluated at 18 thicknesses ranging from 0.01 to 1000 g/cm3 and for the number of nucleons per volume, contained within each material. This research also includes an analysis of the effect of hydrogen storage used within carbon based materials, the effectiveness of Lunar and Martian Regolith as shielding materials, and quantify the effect of using materials containing neutron absorbers: 6Li and 10B.
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HIGH PERFORMANCE LIGHTWEIGHT MATERIALS MADE BY SHEAR ASSISTED PROCESSING AND EXTRUSION (SHAPE)

S. Whalen Scott.whalen@pnnl.gov
For full papers, please enter your abstract here (250 words or less). For lightning talks, ignore this field.
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HYBRID FUEL COUPLING IN A PULSED Z-PINCH ROCKET ENGINE

B. Taylor brian.d.taylor@nasa.gov
The work presented here sought to explore a portion of the parameter space of a hybrid nuclear fuel in regards to ignition and burn by analyzing the effect of initial geometry and thermodynamic conditions. The authors performed 0D power balance and 1D burn wave calculations to determine temperature progression and energy production for defined initial conditions. Geometries examined are representative of concept fuels for a Pulsed Fission-Fusion (PuFF) engine. This work focuses on lithium deuteride and uranium 235 for the fuel since these are seen as leading candidates for PuFF. Presented below is a power balance illustrating a reduction in the energy and density required to breakeven of hybrid fuels in comparison with fusion fuels. Also the impact of fusion and fissile fuel quantities upon initial energies is presented. One can see that the initial energy required to breakeven in a hybrid cylindrical nuclear fuel decreases with decreasing fissile liner thickness, decreasing fusion fuel core radius, and increasing compression ratio of the fusion fuel.
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NUCLEAR HEAT SOURCE CONSIDERATIONS FOR AN ICY MOON EXPLORATION SUBSURFACE PROBE

D. Kramer daniel.kramer@udri.udayton.edu
RTG powered spacecraft have enabled the identification of several icy moons within the solar system which may contain sub-surface oceans of water below a thick ice cap up to tens of kilometers. Inserting a probe into one of these oceans may assist in determining whether Earth is the only place in the solar system where life forms have existed. One concept discussed in the literature is to employ plutonium-238 as a heat source within a probe to melt through the moons ice shell to the liquid ocean. This would then allow the investigation of the ocean environment. This paper discusses considerations for helping to identify potential radioisotope heat source for an icy moon probe, such as: thermal power output, half-life, future availability, etc. Additionally, a first-order analysis infers that two radioisotopes (curium-244 and uranium-232) exhibit a number of the characteristics likely required for a future ocean probe to one of the icy moons. The analysis suggests that compared to the mass of plutonium-238 required, 244Cm could require 75% less mass and 232U would require 88% less mass, while still yielding a similar thermal output. In addition to these options, consideration is given to polonium radioisotopes (Po-208 in particular) as a potential alternative. The authors highly recognize that the selection of any new radioisotope heat source material will require extensive; radiological considerations, realistic evaluation of obtainability, cost factors, and launch safety considerations.
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REVIEW OF IRRADIATION HARDENING AND EMBRITTLEMENT EFFECTS IN REFRACTORY METALS RELEVANT TO NUCLEAR THERMAL PROPULSION APPLICATIONS

N. D. Gaffin, S. J. Zinkle, K. M. Benensky ngaffin@vols.utk.edu
Nuclear thermal propulsion (NTP) is advantageous for future crewed interplanetary missions because of its capability for high specific impulse, thrust, large abort windows, and good cargo capacity. A fuel under consideration for use in NTP systems is a ceramic metallic (cermet) consisting of fissile fuel particles, such as uranium dioxide (UO2) or uranium nitride (UN), suspended in a structural refractory metal matrix, such as molybdenum (Mo) or tungsten (W). When structural materials are irradiated at low temperatures (below ~0.35 times the melting point) to low doses (0.001 to 0.1 displacements per atom), irradiation hardening and embrittlement may occur. This phenomenon increases the yield strength of materials, but also causes a decline in ductility and an increase in the ductile to brittle transition temperature (DBTT). During operation, large temperature gradients are present throughout the core, causing regions of the fuel element to operate at relatively low temperatures and receive neutron doses conducive to irradiation hardening. A comprehensive literature review was conducted to determine the effects of low-fluence neutron irradiation of pure and alloyed Mo and W. Irradiation hardening occurs in Mo and W up to 1070 and 1100 K respectively, with significant changes in the mechanical properties even at very low neutron doses. The reviewed literature relevant to NTP applications are summarized, knowledge gaps identified, and implications of mechanical property evolution on fuel performance and operating margins discussed.
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Lightning Talk

PROCESS DEVELOPMENTS IN FABRICATING U-10MO PLATE FUEL

C. Painter, C. Lavender, J. Vineet Chad.Painter@pnnl.gov
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